The invention relates to a process for cutting through a cable sheathing of fibres with a blade, in which the fibres are brought into a cutting position projecting approximately radially from the cable, and an apparatus for cutting through a cable sheathing of fibres in which the fibres can be brought into a cutting position projecting at least approximately radially from the cable.
Particularly in fibre-optical cables (optical waveguides), a pull relief of KEVLAR (a trademark of DU PONT) fibres or similar fibres having a high tensile strength are frequently provided. In the stripping of such fibre-optical cables, it is therefore also necessary to cut through this fibre layer. The fibres presently used are distinguished by high tensile strength. They are therefore difficult to cut. Conventional stripping apparatuses, for example having stationary V-knives or rotating stripping knives, can therefore be used only with difficulty in most cases for stripping such cables. The safest practical stripping method available today for Kevlar fibres is manual cutting with special scissors.
However, certain machines and apparatuses which are used in particular in an air stream for orienting the fibres in a required direction in order then to cut through the fibres positioned in this manner, by means of, for example, scissors (cf. JP-A-64-3607) or by means of rotating saw blades (cf. DE-A-3925850), have also been developed, in such cases the fibres frequently additionally having to be kept in a fixed position by means of clamping jaws. In all these known apparatuses, an irregular cut is obtained over the circumference of the cable sheathing, because the fibres are pulled in one direction (roughly at right angles to the surface of the sheathing) practically over the entire circumference.
DE-A 3831175 also describes a stripping means having a suction air stream, a suction pipe for receiving the cable being designed in two parts there as a particular embodiment. This can lead to poorly defined cutting of the fibres if fibres in the sheathing are jammed in the suction pipe when the latter is closed and therefore cannot be gripped by the cutting means.
For better understanding, reference is being made here to FIG. 7, which illustrates the prior art. There, the cut fibre ends remaining on the cable sheathing are of very nonuniform length. The fibre ends 30 coming from the right-hand part of the cable 31 have a length of about X2 while the fibre ends 30 coming from the left-hand cable part are only Y2 long. The ratio X2 to Y2 has a high value. In many cases, this is an obstacle in the event of further processing of the cable ends.
Fairly uniform cuts can be achieved by means of apparatuses corresponding to US-A-4914986 or DE-A-3842754. The latter describes a type of saw shearing apparatus which was developed by the applicant and is also capable of cutting a fibrous sheathing all around. However, the mechanical capacity of such an apparatus is relatively great, and at least two separate drives are required. In addition, particularly thin fibres can be relatively easily jammed between the shearing elements, which may lead to a malfunction.
The arrangement described in U.S. Pat. No. 4,914,986 is completely unsuitable for thin fibrous material. This apparatus functions only in the case of braided copper or steel sheaths. In addition, this apparatus too involves a not inconsiderable expense, especially since several components--including radially acting clamping apparatuses--have to be driven.